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Effect of Shiitake (Lentinus edodes) and Maitake (Grifola frondosa) mushrooms on blood pressure and plasma lipids of spontaneously hypertensive rats

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Abstract

To study the effect of Shiitake (Lentinus edodes) and Maitake (Grifola frondosa) on hypertension, spontaneously hypertensive rats (SHR) were fed a diet containing 5% mushroom powder and 0.5% NaCl solution as drinking water for 9 weeks. The dietary mushrooms decreased the blood pressure. The plasma free cholesterol level decreased in Shiitake-fed animals, whereas in Maitake-fed animals the total cholesterol level decreased. There was no difference in the plasma triglyceride and phospholipid levels among the experimental groups. Shiitake feeding resulted in a decrease in VLDL- and HDL-cholesterol whereas Maitake feeding caused a decrease in VLDL-cholesterol only. Plasma LDL-cholesterol was not affected by dietary mushrooms. The results suggest that dietary mushrooms prevent blood pressure increase in hypertension.
I. Nutr. Sci. Vitaminol., 33, 341-346, 1987
Effect of Shiitake (Lentinus edodes) and Maitake
(Grjfola frondosa) Mushrooms on Blood Pressure
and Plasma Lipids of Spontaneously
Hypertensive Rats
Yearul KABIR,1,* Mami YAMAGUCHI, and Shuichi KIMURA2
Laboratory of Nutrition, Department of Food Chemistry, Faculty of
Agriculture, Tohoku University, Sendai 980, Japan
(Received April 2, 1987)
Summary To study the effect of Shiitake (Lentinus edodes) and
Maitake (Grifola frondosa) on hypertension, spontaneously hypertensive
rats (SHR) were fed a diet containing 5% mushroom powder and 0.5
NaCl solution as drinking water for 9 weeks. The dietary mushrooms
decreased the blood pressure. The plasma free cholesterol level decreased
in Shiitake-fed animals, whereas in Maitake-fed animals the total choles
terol level decreased. There was no difference in the plasma triglyceride
and phospholipid levels among the experimental groups. Shiitake feeding
resulted in a decrease in VLDL- and HDL-cholesterol whereas Maitake
feeding caused a decrease in VLDL-cholesterol only. Plasma LDL-
cholesterol was not affected by dietary mushrooms. The results suggest
that dietary mushrooms prevent blood pressure increase in hypertension.
Key Words hypertension, mushrooms, Shiitake, Maitake, spon
taneously hypertensive rat (SHR), plasma lipids, lipoproteins
It has been known for a long time that mushrooms have some medicinal value
and are thus used in Kanpo, Chinese folk medicine. In Kyushu, Japan, the Bukurio
mushroom has been said to contribute to longevity and to cause an increase in
urinary sodium excretion (1). It has been reported that an increase in urinary
sodium excretion caused a suppression of the rise in blood pressure (2). This study
was undertaken primarily to examine the effect of dried Shiitake and Maitake
mushroom powders on the blood pressure of SHRs. These available mushrooms are
an important Japanese food item. There have been some studies on Shiitake and its
extracted hypocholesterolemic substance, but to our knowledge, no studies have
been done on Maitake mushroom. The present paper presents a relationship
between mushroom intake and hypertension in SHRs.
1 ・カ ビ ル , 2 口麻 美,木
* On study leave from Department of Biochemistry , University of Dhaka, Dhaka-2,
Bangladesh.
341
342 Y. KABIR, M. YAMAGUCHI, and S . KIMURA
MATERIALS AND METHODS
Male albino SHRs (from Funabashi farms) of the Okamoto strain (3) weighing
about 116g were divided into three dietary groups of 6 animals each. The three diets
consisted of the following: Group 1 (control), basal diet consisting of 10%egg
protein; group 2, basal diet with addition of 5% Shiitake powders; and group 3,
basal diet with addition of 5% Maitake mushroom powders (Table 1).
The rats were given free access to the diets and 0.5% NaCl solution as drinking
water for 9 weeks. The animals were housed individually throughout the experiment
in stainless steel, wire-bottom cages in a temperature- (24•}2•Ž) and humidity-
(50•}10%) controlled room with a 12-h light/dark cycle. Their body weight was
measured every 4th day and the blood pressure was recorded weekly according to
the tail pulse pickup method using Programmed Electro-sphygmomanometer (PE-
300, Narco Bio-systems, Inc., Houston, Texas). After the 9-week feeding period, the
animals were starved overnight and then sacrificed by ether anesthetization.
The blood was collected from the abdominal aorta in a disposable plastic
syringe coated with heparin and transferred into centrifuge tubes. After being
centrifuged at 3,000rpm for 15min, the plasma was stored in a vial at 0•Ž for later
analysis. The liver, kidney, heart, brain, thyroid, pituitary, and abdominal depot fat
were removed, washed with saline solution and weighed.
The plasma lipoprotein fractions were isolated by ultracentrifugation accord
ing to the technique of Bronzert and Brewer (4). Ultracentrifugation was carried out
Table 1. Composition of experimental diets (%).
a Egg white (54%) and egg yolk (46%). b Ground dried mushrooms. c Five grams of
soybean oil contain 100 I. U. of vitamin D. d Compositions were described by Harper (11).
e One gram of fat-soluble vitamin mixture contains vitamin A 1,500 I. U., vitamin E
10mg, p-aminobenzoic acid 10mg, choline chloride 150mg.
J. Nutr. Sci, Vitaminol.
EFFECT OF MUSHROOMS ON SHR 343
in a Hitachi 70P-72 ultracentrifuge using a RPL42T rotor at the density of plasma
(d=1.006g/ml) and at a solvent density of 1.060g/ml respectively, by addition of
KBr. The levels of total cholesterol, free cholesterol, triglyceride, phospholipids in
the plasma and cholesterol levels in its lipoprotein fraction were measured by using
assay kits (Wako Chemical Industries, Ltd., Osaka).
Statistical analysis: Data were treated statistically using Student's t-test, and
where t-test was not possible Cochran-Cox test was followed.
RESULTS AND DISCUSSION
As shown in Fig. 1, the rats fed mushrooms were significantly low in growth
compared to the control. The difference was more considerable (p<0.001) in
Maitake-fed animals than in those fed Shiitake (p<0.05) when compared with the
control. The systolic blood pressure of rats fed either Shiitake or Maitake was also
significantly lower (p<0.001) than that of the control (Fig. 2). It is possible that the
lower body weights due to mushroom diets may have had some effect on the
lowering of the blood pressure. But previous works in this laboratory (5) showed
that change of body weight had no effect on the blood pressure.
The tissue weights of the sacrificed animals are summarized in Table 2. The
weights of depot fat and the heart were significantly lowered by feeding Maitake.
The plasma cholesterol, triglyceride, and phospholipid levels are shown in
Fig. 1. Body weight changes in spontaneously hypertensive rats fed mushroom diets.
Body weights are represented as the mean•}SE for 6 rats. Significantly different
from control, * p<0001, ** p<0.05.
Vol. 33, No. 5, 1987
344 Y. KABIR, M. YAMAGUCHI , and S. KIMURA
Fig. 2. Systolic blood pressure changes in spontaneously hypertensive rats fed mush
room diets. Blood pressure levels are represented as the mean•}SE for 6 rats .
Significantly different from control , * p<0.001, ** p<0.01
.
Table 2. Effect of mushrooms on final body and organ weights of SHRs .
Each value represents mean•}SE for 6 rats . Significantly different from control,
* p<0 .001, ** p<0.01, *** p<005
Table 3. The total cholesterol level in the rats fed Shiitake was nearly equal to that
of the control, but the free cholesterol level was significantly lower (p<0 .01) than
that of the control. An explanation is that Shiitake may have raised the esterifi
cation of plasma cholesterol, i.e. increased the activity of lecithin: cholesterol
J. Nutr. Sci. Vitaminol.
EFFECT OF MUSHROOMS ON SHR 345
Table 3. Effect of mushrooms on plasma cholesterol, triglyceride, and phospholipid
levels in SHRs.
Each value represents mean•}SE for 6 rats. Significantly different from control,
* p<0 .001, ** p<0.01, *** p<0.05.
Table 4. Effect of mushrooms on cholesterol levels in plasma lipoproteins of SHRs.
a VLDL include chylomicrons . Each value represents mean•}SE for 6 rats. Significantly
different from control, * p<0.01.
acyltransferase (LCAT). In fact, a higher activity of plasma LCAT in Shiitake-fed
rats has been previously reported by Tokuda et al. (6). They have also reported (7) a
decrease in plasma cholesterol levels by feeding Shiitake, whereas we could not find
any change in the plasma cholesterol level in SHRs. This is presumably due to
genetic variation in the SHR strain or in the experimental conditions. In fact, SHRs
generally have low plasma cholesterol levels (8, 9) and have an abnormality in lipid
metabolism, especially in cholesterol synthesis, as previously described (9).
On the other hand, in the Maitake group the plasma total cholesterol level was
significantly low (p<0.01) compared to that in the control (Table 3). This result
indicates that feeding Maitake is much more effective in reducing the plasma
cholesterol levels in SHRs. This may be due to the increase in cholesterol excretion
or/and inhibition in cholesterol synthesis. No significant difference in plasma
triglyceride and phospholipid levels was observed in any of the 3 groups.
The cholesterol levels in each lipoprotein fraction are shown in Table 4. The
VLDL- and HDL-cholesterol levels of Shiitake-fed rats were significantly lower
(p<0.01) than those of the control, whereas in Maitake-fed rats, only the VLDL-
Vol. 33, No. 5, 1987
346 Y. KABIR, M. YAMAGUCHI , and S. KIMURA
cholesterol level was significantly lower (p<0 .01). Dietary mushrooms had no
significant effect on LDL-cholesterol . The lower level of VLDL- and HDL-
cholesterol after Shiitake feeding has been reported previously (6). The reason for
this decrease is not known . The alteration in the lipid and lipoprotein metabolism in
SHRs seems to depend upon genetic variation which might occur during the
selection of animals when establishing SHR (10). However, our results suggest that
the dietary Shiitake and Maitake prevent the increase of blood pressure in SHRs.
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A method is described for the reliable, fast, and relatively inexpensive fractionation of plasma lipoproteins and quantitation of their cholesterol content. This procedure requires 350 microliter of plasma and can be completed within 3 h. Plasma lipoproteins (175 microliter of plasma) were prestained with Fat Red 7B and centrifuged (Beckman Airfuge) at plasma density (d = 1.006 kg/liter) and at a solvent density of 1.060 kg/liter, adjusted by adding solid KBr. Prestained centrifuged samples demonstrated the characteristic elevation of chylomicrons in phenotypes I and V, low-density lipoproteins of phenotype II, very-low-density lipoproteins in phenotype IV and V, and continuum of pink color throughout the centrifuge tube, diagnostic of the floating beta lipoprotein of type III. Centrifuged samples were separated into top and bottom fractions by aspiration. Cholesterol was quantitated with an enzymic oxygen-electrode analyzer (Beckman Cholesterol Analyzer). Correlation coefficients between cholesterol values for plasma from normal hyperlipidemic individuals obtained with the Beckman Analyzer vs. the Technicon AutoAnalyzer II and SMAC systems were 0.977 and 0.973, respectively.
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Genealogical study and experimental fat-cholesterol and salt loadings showed that the present strain (F26-27) of spontaneously hypertensive rats consisted of several substrains with no difference in the level of blood pressure but with a marked difference in the incidence of cardiovascular lesions. Biochemical specificities of these substrains were demonstrated by ALPase and esterase isozymes in the liver and serum. Different responses in serum cholesterol level to the hypercholesterolemic diet served as a further differentiation of some lines among these substrains and were seemingly related to their vulnerability to cardiovascular lesions under these experimental conditions.
Effects of dietary protein levels and umami on the palatability to saltiness in rats (II)
  • Y Yokomukai
  • M Komai
  • S Kimura
Yokomukai, Y., Komai, M., and Kimura, S. (1984): Effects of dietary protein levels and umami on the palatability to saltiness in rats (II), Proceedings of the 18th Japanese Symposium on Taste and Smell, pp. 113-116, November.
Effect of dietary protein on blood pressure and renal function in spontaneously hypertensive and control rats
  • T Kanamaru
  • N Nakanishi
  • N Igarashi
  • M Kato
  • S Kato
  • N Sugino
Kanamaru, T., Nakanishi, N., Igarashi, N., Kato, M., Kato, S., and Sugino, N. (1986): Effect of dietary protein on blood pressure and renal function in spontaneously hypertensive and control rats. J. Hypertension, 4 (suppl 3), 5457-5458.